Removing tar from PVC stink pipes & metal vents?

All the vent flashing and stink pipe boots have been visited by the "tar monster" ... can i get this stuff off enough to install new rubber boots, or do I need to cut the pipe and join a new section in?

Dawn dish soap is safer, WD, oils, gasoline are all bad for your hands, they soak directly into your skin and to your liver. Plus the dish soap won't discolor or damage the roofing materials if you spill some.